Field of the Invention
The present invention relates to an image pickup apparatus, a control method therefor, and a storage medium, and in particular to an image pickup apparatus capable of calculating light amount changing characteristics of an object and enlarging a dynamic range.
Description of the Related Art
Conventionally, image pickup apparatuses such as digital cameras reduce unevenness of exposure arising from periodical changes in the amount of light from an object caused by, for example, lighting through alternating current. For example, there is an image pickup apparatus which stores electric charge in a photometric device of an electric charge accumulation type for a first accumulation period for photometric measurement or a second accumulation period for detecting flicker arising from periodical changes in luminance of a light source. This image pickup apparatus performs photometric measurement based on output from the photometric device in which electric charge was stored for the first accumulation period and detects flicker based on output from the photometric device in which electric charge was stored for the second accumulation period (see Japanese Laid-Open Patent Publication (Kokai) No. 2012-235325).
There is another image pickup apparatus which causes an image pickup unit to perform accumulation for flicker detection so as to detect a frequency of power supplied to a light source which causes flicker in an image and perform accumulation for normal image pickup other than accumulation for flicker detection (see Japanese Laid-Open Patent Publication (Kokai) No. 2013-42298).
There is still another image pickup apparatus which measures a light emission cycle and phase of a light source, and in accordance with the light emission cycle of the light source, causes an electronic shutter and a mechanical shutter to operate in synchronization with each other at the time when the amount of light increases (see Japanese Laid-Open Patent Publication (Kokai) No. 2004-193922).
On the other hand, there is an image pickup apparatus which has an image pickup device having a plurality of pixels differing in terms of sensitivity so as to enlarge a dynamic range in an image obtained as a result of shooting. This image pickup apparatus generates an image with a wide dynamic range by a single exposure.
However, calculation of light amount changing characteristics of an object such as detection of flicker and enlargement of a dynamic range during photometric measurement are not compatible, and when an attempt is made to enlarge a dynamic range during photometric measurement, it is difficult to calculate light amount changing characteristics of an object with high accuracy.